Process for preparing printing-plates by means of electrolytic etching.



H. STREGKER-AUFBRMANN.

PROCESS POE PEEPARING PRINTING PLATES BY MEANS 0E ELEGTEOLYTIG ETGHING.

APPLICATION FILED DBO. 13, 1906.

909,831 Patented Jan. 12, 1909.

Egl' Fig, 3.

HANS STRECKER-AUFERMANN, 0l" MUNlCtt, GERMANY. I

PROCESS FOR PREPARING.PRINTING-PLATES BY MEANS OF ELECTROLYTIC ETCHING.

Specification of Letters Patent.

Patented Jan. 12, 1909.

Application tiled December 13, 1906. Serial No. 847,635.

To all 'tu/tom 'it 'muy concern.' t

Be it known that I, HANS S'rnnonnn- AnrnniuANN, llmperor, and resident of Munich, Germany, have invented certain new and useful Proeesses for lreparing Printing llates b Means of lllectrolytie Etching, of which the following is a specification.

This invention -rclates to an clcctrolytic process of etching ready for printing, lates and printing rollers made of any metal) as iron, steel, nickel, copper, brass, zinc and the like, this etching being accomplished in the usual way. f

The met al plates or rollers which are provided with a layer sensitive to light and upon which an image has been copied by applying a photographic negative thcreover and exposing, said layer being formed of chrome gelatin, chrome glue, chrome albumin, chrome fish glue, chrome gum arabic or similar substancesl or of a mixture of these materials, with or Without raining, are placed as :modes in a bath with their layers directed towards a cathode. A screen may be copied into the layer or it may contain a simple. line drawing. The layer acts as a diaphragm which allows of the free exchange of the ions.

Any concentrated solution which has a swelling but not dissolving action u on the layer of chrome glue or the like may e used as the electrolyte.

The concentrated solutions of the metal chloride are well adapted for this purpose such for example, as ferrie chlorid or chlorids of zinc, copper and aluminum.

The process can be advantageously carried out, by means of the apparatus shown in the accompanying drawing, in which- Figure 1 is a perspective View showin"r a simple arrangement of the apparatus an Figs. 2, 3 and l are similar Vlews showing sli htl different arrangements.

n a 1 the figures the image surface which is equivalent to the anode has been designated by A, the cathode by B, the electrolyte by C, th'e source of electrical supply by D and the receptacles, in which thev anode and the cathode are susple'nded, F. i l Accordin to .t e sim'p e arran `'ement shown by tig. 1, the plate A, whic it is desired to etch and which carries the faintly visible layer is connected by.a conducting a subject of the German suchl wire with the positive .pole of the dynamo and the cathode l is connected by a second wire with the negativo pole of the dynamo.

'lhe plate A carrying the co v et the image is protected at its borders vtrom the etching action by a coat ot' lacquer, and is suspended as the anode in the bath (l. 'lhe material ot the cathode l may be of any hind desired. The electrolyte used is a eoncentrated vaqueous solution otl one of the above cited swelling but not dissolving agents. After about 5 to 15 minutes, during which time the circuit. may be open or closed, the layer composed ot glue or the like swells to ditl'erent. thicknesses according to the nuage. When the circuit has previously been interrupted, it is now closed and the etching operation begins, the ions ot the acid wandering to the metal through the layer as a diaphragm while dissolved metal goes to the cathode. As the current, according to the thickness of the layer, which varies according to the more or less strong exposure of the parts, reaches the metal more or less easily, a true ctcl'iing is obtained which produces the image exactly.

The process may also be very advantageously carried out by arranging any desired number of etching )lates B A, BA, BA between the anode A and the cathode B, the layers of these plates which are to be etched, being all directed towards the cathode and, consequently, are anodic while the back sides of the plates which remain uncovered and must not be lacquered, are directed towards the anode and therefore are cathodic. All the anodic sides are etched, while the dissolved metal is precipitated upon the cathodic sides, or hydrogen is set 'free thereupon when certain electrolytes are used. In this arrangement', only the extreme anodes A are connected with the positive pole of the engine and the extreme cathodes with the negative pole. The intermediate plates have their image, which in the drawing is scarcely visible, directed towards the cathode, the image side being anodi'c. l

The strength of the current must be held in this process between low limitsl and varies according tothe tineness of the iinaee between 0.05 and 2 amperes per square centrl meter.v The electrolyte generallyconsistsof 'ferrie chloridof 42 to 30 Baume. Ihe degree of concentration of the bath is high,

. from the cathode chamber by av diaphragm and Vusing a weak solution in the cathode chamber, the solution in the anode chamber f being concentrated. This arrangement has been shown by Fig. 4. This apparatus comrises two cells or baths which are connected 1n parallel. The second bath contains a diaphragm E and the solution C2 1s more con- Y centi-ated than the solution C1. During the electrolysisthe solutions diffuse through the diaphragm'and solution C2 is thereby more and more diluted. The degree of concentra'- tion of C1 and C2 is consequently compensated by dili'usion, the solution contained in the anode chamber gradually becoming more diluted. Here also, it is impossible to give determined rules; the process must be carried out according to other well known indications.

It is sometimes advantageous to cause the current to beinterrupted by meansof an interrupter instead of permitting it to act continuously.

The plate, after the etching has been completed is cleaned by means of hydrate of sodium or similar material,whereafter it is sub'ected to another etching o eration carrie out in the usual or.n tiie above described manner.

It is not always necessary in my process to introduce the currentV from an external source. It is on the other hand, ossible, as in the well known Daniell cell, to ave a zinc plate provided with a layer of chrome glue or the like and with a cop of the ima e andV to dipV it into a solution o sulfate or c ilorid of zinc, or ferrous chlorid and to arrange opposite it a copper or lead plate contained in a porous cell containing a suitable de olarizing iuid so that acell is obtained which has zinc and copper as poles and a diaphragm. n l

An apparatus suitable for this purpose has been shown by Fig. 3. This apparatus forms a primary element in the cell of which a diaphragm is introduced. Each of thetwo compartments or cells thus formed is filled with an electrolyte C1 C2 having a di'erent com osition. Suspended in the anode chamber 1 is a zinc plate to be etched and which carries the image layer, while in the cathode chamber C2 hangs the otherr metallic plate as for instance copper plate.

The liquid consists of a depolarizing fluid. Both plates are connected by means vof wire. With a view of preventing precipitation 'of ferrie hydroxid which when zinc is etched, would be formed behind theimage la er ferric chlorid is used with 'ferricyani 'of potassium, oxalic acid, sugar, glycerilnhctA ric acid, tartarie acid, or acetate of sodium.

that is to say not only or the Daniell cell arrangement, but also when the current is conveyed from an external'source.

Having now fully described my said invention what I claim and'desire to secure by Letters Patent is:

1. Process of'preparing printing plates or rollersV by means of ele'ctrolytic etching,

yThis precaution may be' generally employed, Y

consisting in coating a Ymetal plate or roller f on one side with a layer of chromeV colloidal -with a layer of-c rome colloidal material,

copying an image into the said layer by exposing it to the action of light behind a suitable negative and using the thus Vpre- I paredvplateV or roller as an anode in an electrolytic bath, the electrolyte whereof comprises a concentrated solution of a chlorid which is a swelling but non-dissolving agent for the saidk chrome colloid layer, the cathode being of any suitable metal, substantiallyV as and for the purpose set forth.

3. A process of preparing printing plates or rollers by electrolytic etching, consisting in coating a metal late or roller on one side with a. layer of c rome colloidal material,

copying an image into the said layer by exposing it to actionr of the light behind a. suitable negative and using the thus prepared plate or roller as an anode in an electrolytic bath, the electrol te whereof comprises a concentrated solution of fer-ric chloridthe cathode being of any suitable metal, substantially as and for the purpose set forth. A

4. A processof preparing printing platesk or rollersiby electrolytic etching, consisting in coating a metal plate or roller on one side with a layer of chrome colloidal material,copying an image into the said layer exposing it to the action ofV light behind a suitabl ne ative, covering the bor-V ders of the sai plate or roller with a coating of lacquer and using the plate or roller thus obtained as an anode in an electrolytic bath the electrolyte whereof comprises a concentrated solution of a chlorid which is Y a swelling but not a dissolvin agent for the said chrome colloidal layer o the anode, the cathode being formed of any suitable metal,

substantially as, and for the purpose set forth. 4 f

iio

5. A process of preparing printing plates or rollers by electrolytic etching, consisting in coating` metal plates or rollers on one side with a layer of chrome colloidal material, copying an image into the said layer by exposing it to the action of the light behind a suitable negative using the said plate as an anode in an electrolytic bath, the electrolyte whereof comprises a solution of a chlorid which is a swelling but not a dissolving agent for the said chrome colloidal material, and which is supplied with direct current from an outside source, substantially as and for the purpose set forth.

6. A process` of preparing printing plates or rollers by electrolytic etching', consisting in coatingT a metal plate or roller on one side with a layer of chrome colloidal material,

copying an image into the said layer by exposing it to the action of the light behind a suitable negative, using the said plate or roller as an anode in an electrolyzing de- Vice, the electrolyte whereof comprises a solution of a swelling but not a dissolving agent for the said chrome colloidal mate'- rial, and which is supplied with direct current 'from an outside source and provided with means for abruptly interrupting the current, substantially as and for the pur-4 pose set i'orth.

In testimony whereof I have hereunto set my hand in presence of two Witnesses.

HANS S'lRllCKER-AUFERMANN. lVitncsses:

- Louis I. MUELLER,

MATIHLDE K. HELD. 

